1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly to an LCD device having a transformer and a ferrite core plate disposed between a printed circuit board and the transformer.
2. Discussion of the Related Art
Flat panel display (FPD) devices have a relatively light weight, a thin profile, and low power consumption characteristics are and thus are commonly used instead of cathode ray tube (CRT) devices. Further, display devices are generally classified into emissive display devices and non-emissive display devices. In more detail, emissive display devices display images by emitting light themselves, while the non-emissive display devices require an additional light source because they do not emit light by themselves. For example, plasma display panel (PDP) devices, field emission display (FED) devices, and electroluminescent display (ELD) devices are classified as emissive display devices. Further, LCD devices are classified as non-emissive display devices and are commonly used in notebook and desktop computers because of their high resolution, capability of displaying colored images, and high quality image display.
In addition, the LCD devices include an LCD panel for displaying images and a backlight unit for supplying light to the LCD panel. The LCD panel includes two substrates facing each other with a liquid crystal material interposed therebetween. Further, liquid crystal molecules of the liquid crystal material have dielectric constant and refractive index anisotropic characteristics due to their long, thin shape, and an orientation of the liquid crystal molecules is controlled via a voltage applied to electrodes formed on each substrate. Thus, a transmittance of the LCD panel is changed according to polarization properties of the liquid crystal material.
Also, a backlight unit is used as the additional light source for the LCD panel and is disposed under the LCD panel such that the LCD device displays images using light produced by the backlight unit. In addition, backlight units are generally classified as a side-type backlight unit and a direct-type backlight unit. The direct-type backlight unit includes a plurality of light sources and is commonly used to provide an increased brightness.
Further, discharge lamps such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) are used as light sources in the backlight unit. Light emitting diodes (LEDs) are also being used more often as the light source of the backlight unit to improve a color reproducibility and to increase a brightness of the display.
In more detail, FIG. 1 is a cross-sectional view showing a direct type LCD module 1 according to the related art. As shown, the LCD module 1 includes an LCD panel 10 and a backlight unit 20. Further, the LCD panel 10 includes first and second substrates (not shown) facing each other with a liquid crystal layer (not shown) therebetween. The backlight unit 20 is also disposed under the LCD panel 10.
The LCD module 1 also includes a main frame 40 supporting edges of the LCD panel 10 and the backlight unit 20, a top frame 60 supporting a front edge of the LCD panel 10, and a bottom frame 50 covering a backside of the backlight unit 20.
As shown, the backlight unit 20 includes a reflective sheet 22 covering an inner surface of the bottom frame 50, a plurality of fluorescent lamps 24 arranged in parallel to each other on a front surface of the backlight unit 20, and a plurality of optical sheets 28 between the plurality of fluorescent lamps 24 and the LCD panel 10. In addition, the LCD panel 10 receives light emitted from the plurality of fluorescent lamps 24, in which the light is modified so as to have a uniform brightness.
Further, a backlight driving circuit (not shown) is disposed on a printed circuit board 70 and is used for driving the fluorescent lamp 24. In more detail, the backlight unit driving circuit includes an inverter (not shown) for turning the fluorescent lamp 24 ON and OFF. The inverter includes at least one transformer 72 that amplifies and outputs an alternating current (AC) input voltage. In addition, as shown in FIG. 1, the printed circuit board 70 having the backlight driving circuit is closely adhered with the bottom frame 50 via a bended portion bending back toward a backside of the bottom frame 50.
Further, the plurality of fluorescent lamps 24 are arranged in a row, which reduces the required number of the invertors and lowers the production cost of the LCD panel. However, with the increase of fluorescent lamps, the capacity of the transformer 72 is also increased. For example, the capacity of the transformer 72 for a 32 inch display is about 65 Watts more than the related art value of about 10 Watts.
Furthermore, when the capacity of the transformer 72 is increased, a leakage magnetic field from the transformer 72 is also increased. In more detail, an exothermic phenomenon under a high temperature occurs due to an eddy current in the adjacent bottom frame 50 and a consumption power is increased, which reduces an efficiency of the transformer 72. Particularly, the leakage magnetic field is increased because the bottom frame 50 is generally formed of a steel material such as electro-galvanized iron (EGI).